Vehicle safety ratings are an important factor in the design of a vehicle and can have significant impact with regard to governmental approval and decision making by purchasers of vehicles, among others.
One particular element for establishing a vehicle's safety rating relates to head injury criterion (HIC). HIC may be evaluated both for the driver and passengers of a vehicle, as well as for third-parties who may become involved in a collision with the vehicle, e.g., pedestrians, cyclists, motorcyclists, etc.
In order to test HIC for a vehicle, adult and child “headforms” (i.e., an impactor) are subjected to impacts at various angles of impact at various areas on the hood of a vehicle at a predetermined speed, and the results for each impact recorded.
Values for HIC may be calculated based on an accelerometer installed in the impactor according to equation (1)
                    HIC        =                              {                                                            [                                                            1                                                                        t                          2                                                -                                                  t                          1                                                                                      ⁢                                                                  ∫                                                  t                          1                                                                          t                          2                                                                    ⁢                                                                        a                          ⁡                                                      (                            t                            )                                                                          ⁢                        dt                                                                              ]                                2.5                            ⁢                              (                                                      t                    2                                    -                                      t                    1                                                  )                                      }                    max                                    (        1        )            where t1 and t2 are the initial and final times (in seconds) of the interval during which HIC attains a maximum value, and acceleration a is measured in gs (standard gravity acceleration).
In the past, car manufacturers have installed pedestrian protection airbags or active hood systems to enhance the pedestrian protection features. Such active systems can be costly and difficult to design/construct.
In addition to active systems, passive designs have also been implemented. However, while such passive systems are less expensive, there is a desire to continually to improve such systems so as to reduce the possibility of injury.
JP 2007-331521 discloses a duct part of an outside air introducing duct for a vehicle that is deformable and crushed by a load from an upper part.